Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effec-tively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is pro-posed that includes three stages:multi-factor analysis,adaptive decomposition,and an optimization-based ensemble.First,considering the complex factors affecting DO,the grey relational(GR)degree method is used to screen out the environmental factors most closely related to DO.The consideration of multiple factors makes model fusion more effective.Second,the series of DO,water temperature,salin-ity,and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform(EWT)method.Then,five benchmark models are utilized to forecast the sub-series of EWT decomposition.The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm(PSOGSA).Finally,a multi-factor ensemble model for DO is obtained by weighted allocation.The performance of the proposed model is verified by time-series data collected by the pacific islands ocean observing system(PacIOOS)from the WQB04 station at Hilo.The evaluation indicators involved in the experiment include the Nash-Sutcliffe efficiency(NSE),Kling-Gupta efficiency(KGE),mean absolute percent error(MAPE),standard deviation of error(SDE),and coefficient of determination(R2).Example analysis demonstrates that:① The proposed model can obtain excellent DO forecasting results;② the proposed model is superior to other comparison mod-els;and ③ the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.